1. Field of the Invention
The present invention relates, in general, to a construction method for the metal wiring of semiconductor device and, more particularly, to a method for forming a tungsten plug on a contact hole.
2. Description of the Prior Art
A blanket tungsten chemical vapor deposition (blanket-W CVD) for the formation of tungsten plug for metal wiring, which is to deposit tungsten entirely over a substrate, generally comprises a glue layer deposition process and an etch back process for the tungsten film entirely deposited. The tungsten etch back process is carried out by a plasma etch, a dry etch.
When the plasma etch back for the plug formation is carried out, there is often generated an imperfection, which leaves on a region some tungsten which must be removed by etch. In turn, these tungsten residues cause the bridge and short of a metal layer.
In order to prevent the formation of the tungsten residues, the etch back may be overly performed. However, this over etch causes the excess removal of the tungsten from a contact plug and has a key hole formed on the center of the contact hole, so that the metal wiring formed comes to be poor in reliability.